WO1999060443A2 - Laser projection apparatus with liquid-crystal light valves and scanning reading beam - Google Patents
Laser projection apparatus with liquid-crystal light valves and scanning reading beam Download PDFInfo
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- WO1999060443A2 WO1999060443A2 PCT/US1999/009501 US9909501W WO9960443A2 WO 1999060443 A2 WO1999060443 A2 WO 1999060443A2 US 9909501 W US9909501 W US 9909501W WO 9960443 A2 WO9960443 A2 WO 9960443A2
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- laser
- projector
- light
- image
- projection
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/005—Projectors using an electronic spatial light modulator but not peculiar thereto
- G03B21/006—Projectors using an electronic spatial light modulator but not peculiar thereto using LCD's
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/22—Telecentric objectives or lens systems
Definitions
- This invention relates generally to devices for 0 projecting pictures onto large viewing screens; and more particularly to such devices that project laser beams via reflective liquid-crystal light valves to form such pictures.
- the invention has its most important applications in such projection of moving pictures.
- nonlaser light sources With nonlaser light sources, this concern is compounded when taking into account the additional surcharge for optical energy that is visible but goes off in directions other than into the collecting optics of a projector.
- Most non- laser sources incandescent hot-filament or arc lamps) radiate approximately equally in all directions .
- the amount of visible light that can be directly collected from such a source into an optical system is typically less than a tenth of the visible light produced. It can be dismaying to pay for many times the amount of electrical energy used — even that which is directly used to make visible light, setting aside consideration of the conversion efficiency discussed above. Therefore it is common to provide reflectors behind the source, or more generally speaking to try to surround the source with reflectors to help capture a greater geometrical fraction of the visible energy.
- spectral components can be controlled so that minimal energy is wasted in infrared or ultraviolet radiation.
- a laser is therefore far more energy efficient than other sources — with respect to both raw conversion efficiency of electricity into visible light and geometrical capture of that visible light. Lasers and their power supplies do give off heat, and this must be managed. In comparison with a typical arc lamp or like device, a laser is vastly more' favorable with respect to the amount of heat, the temperature involved, and the difficulty of collection.
- Contrast is enhanced by avoiding such crosstalk — or in other words preventing the spill of a cast over an entire image frame, from bright image areas. Such undesired spill corrupts areas that should be dark . Further enhancement of just the same sort arises from the inherent collimation of a laser beam.
- the final optical stage i . e. , the projection lens — is preferably broadband since it preferably carries all the colors in a common beam; for this purpose a high-quality achromat is desired.
- each distinct beam carrying a separated spectral segment is already broadband, either complicating or degrading the effectiveness of all optical effects or manipulations .
- More significant to contrast enhancement is the relative sharpness (i . e. , narrowness of angular range) of laser polarization, in comparison with polarization obtained through a common polarizer. Because of this, in areas of a $ latent image that should be bright (calling for passage of a beam through the downstream polarizer) , the polarization state provided when using a laser source is defined more sharply; the same is true for areas that should be bright and call for extinction. The latent image therefore is 0 potentially brighter where it should be bright, and darker where it should be dark — or, in other words, has better contrast.
- a spatially modulated beam can carry an image over a long distance without becoming blurry.
- this performance characteristic may be more associated with favorable divergence properties than with collimation.
- the capability of a good arc-lamp-based projector to produce a sharp image at a distance may be about as good as a laser-based system heretofore — provided that the image is projected onto a screen or other viewing surface that is:
- the prior-art laser projector may have little advantage in sharpness as such if the projection medium is all at the same distance from the projector, and there is an opportunity to adjust the projector for the actual projection distance.
- infinite fo- cus is a misnomer, in that "focus” refers to formation of an image at a preset “focal plane” (sometimes in the retina) by convergent light rays from various parts of a lens system. Such convergence requires adjustment of the optical system for a specific projection distance — a process with which of course nearly everyone is familiar.
- Infinite focus derives from the concept of "depth of focus”, combined with the idea that laser-transmitted images seem to have infinite depth of focus.
- each pencil of rays from the laser carries a specific, fixed part (e. g. pixel) of the image.
- Laser beams are initially collimated so that the ray pencils are all parallel, never crossing one another or converging. It is possible to force a laser beam to converge to a rather fine point (of course only an approximation of a point) by interposition of a lens that does focus all the rays. For present purposes it would not make sense to do this, since there would be no image — only a single bright spot — and indeed this is never done in a system that displays the "infinite" effect.
- the spatially modulated beam is simply directed to a viewing medium, where the ray pencils are stopped and so make the impressed image visible to viewers.
- a substantially conventional lens may be employed — and within the constraints of pixel or raster-line visibility the image will be sharp but never "focused".
- the other half of the phrase "infinite focus” is also somewhat inaccurate since there are some limits to the depth, along the projection direction, at which images appear sharp. These limits are imposed by beam divergence and other diffraction effects.
- spot size does change, to the extent that the beams are spread out on a viewing surface that is angled to the projection beam.
- audience position — I . e. whether the audience is looking essentially along the projection direction or along a normal to the surface, or from some other direction — the stretching may not be visible in its entirety, or at all.
- the beams may be amplitude modulated for more complex effects , and the beams may be combined into a composite beam that is swept as a unit — in which case the entire resulting image may enjoy infinite sharpness provided that the beams are simply projected and not focused.
- vector-graphics projection is of only secondary interest for present purposes .
- Raster-scanning systems The topic now turns to reproduction of whole picture images that are generalized, in the sense that the projection system is a neutral vehicle for display of any raster-based image.
- the projection- system raster can be set to match traditional or conven- tional broadcast television, whether U. S. interlaced or otherwise, or to match a high-definition television format — or to match a conventional computer-monitor format, or any other well-defined raster specification.
- the compressions and rarefactions of this input modulation in the AOM create or write a phase-retardation pattern within the crystal , extending transversely from one side of the crystal to the other and representing optical modulation in one primary color for an entire video raster line.
- a laser is pulsed to provide a light beam intersecting the pattern at right angles .
- This reading-beam pulse length is very short compared with the propagation speed of the acoustic wave through the crystal, so that in effect the laser illumination is able to stop the motion of the raster line.
- the laser beam in effect reads the entire retardation pattern, and upon leav- ing the crystal has impressed upon it — in phase retardation — a latent image of the entire raster line.
- This image is then developed, as suggested earlier, by a polarization analyzer or equivalent, downstream of the crystal.
- the result is an image of one primary color compo- nent of the raster line, which is then preferably combined with like images for the other two primaries, formed in separate AOMs .
- each of the three individual primary-color laser beams or the composite beam must be shaped to form a wide, shallow beam cross-section.
- a more-common beam aspect ratio in passage through the modulators — i . e. , to perform the shaping after the beam has passed through the modulators, though before the final projection lens.
- the composite beam is enlarged and projected to a particular position vertically on a viewing screen, forming a three-color raster line for viewing by the audience.
- the process is repeated for successive lines — but shifting the vertical position progressively down the screen — to construct an entire image frame, and then for subsequent frames to produce moving pictures.
- each raster line is controlled by a rotating polygon or other vertical-sweep device, so that successive lines are displaced to successive appropriate positions on the screen.
- This sweep it is important to note, follows the modulators — i . e. is introduced downstream, along the optical path, from the modulators — as exemplified, for instance, by U. S. 5,255,082 of Tarnada, assigned to Sony.
- the pulsed beam on which this modulation is impressed must necessarily correspond in shape to the wide, shallow aspect ratio of one raster line. It would not be possible to operate a one-raster-line-at-a-time modulating system with any other beam shape.
- the optical system must include an optical stepper or continuous scanner of some sort — to shift the target position successively down the viewing screen for the successive raster lines, as described earlier.
- Even a continuous scanner, in this type of system amounts to a stepper since the beam is pulsed only intermittently, once per raster line. It would not be possible to operate a one-raster-line-at-a-time modulating system without some sort of stepper.
- Speckle This well-known term describes a now- familiar phenomenon of laser illumination, a coarse and very bright granular pattern of light that shimmers with tiny movements of the viewer's eyes. Speckle is highly undesirable in image projectors for displaying ordinary pictures (movies, television shows etc.) because it pervades the images and distracts from the informational or dramatic content of the show.
- speckle is an interference pattern formed within the eye. Although in principle present with other sources too, speckle is not ordinarily visible with such sources. Those skilled in the art recognize that the speckle effect can be made negligible by introducing various kinds of either phase confusion or . relative motion, as between the laser source and the eye.
- Hargis introduce ces several approaches, "each of which introduces an optical path randomizing [medium] at an intermediate . . . plane within the projection optics".
- Provision of his illustrated device, plus a system of electromagnets and associated electrical drive, may not be expensive but it is certainly elaborate and surely diffuses — and thus randomly redirects and wastes — expensive laser energy.
- Tamada For example, U. S. 5,255,082 of Tamada, assigned to Sony, strongly rejects use of laser lines in the region of 647 nm for a primary red beam. Tamada offers the reasoning that such wavelengths should be avoided because they are weak in the spectra of certain lasers which he prefers .
- red light component produced by the krypton ion laser requires four-to-five times the power as the comparable power of an [argon] ion laser. . . .
- the krypton red light component is at a wavelength that the human eye is not as sensitive to and therefore makes it difficult to balance with the other colors to give a complete color scale with reasonable power.
- the [argon] ion laser in combination with a dye laser is therefore preferred . . . .
- the dye laser preferably converts light energy of a shorter wavelength to a longer, tuneable wavelength.”
- Laser types proposed or used It is well known, at least in concept, to employ lasers of a great number of different types for laser projectors. In particular it is known to employ gas, dye and solid-state lasers in this field.
- gas Many subtypes are known, but foremost in this category are argon lasers for spectral-line groups in the blue and green, and krypton lasers for red. Thus argon gas laser beams are commonly split for separate modulation in separate AOMs that receive blue and green image-data components, while a krypton gas laser beam is modulated in a third AOM that receives red image-data components .
- dye lasers are of particularly great value because they are tunable (particularly to 610 nm) .
- reliance on tunability is a handicap because of the extra operator attention which it demands, as well as the high cost of tunable mirrors and other needed paraphernalia.
- Dye lasers are considerably less user-friendly than gas lasers, on account of their requirements for management of an additional pumping stage at the front end and mixing stage at the back. In most cases they also consume profli- gate amounts of extra energy in generating light at frequencies that are not wanted but merely needed for purposes of subtraction or addition to obtain desired frequencies. This waste may be acceptable in high-end consumer or boardroom equipment, where literally conspicuous consumption can be a virtue. It is highly questionable, however, in a cost-conscious commercial environment, for example a light- hungry projector system for driving a mundane IMAX®-style screen or an outdoor-spectacle system which projects images onto, actually, monuments and other structures.
- Liquid-crystal “device” modulators Unlike the AOM, a liquid-crystal “device” or “display” (LCD) modulator provides modulation over an entire frame. Here it is possi- ble to flood an entire frame at a time, and project the resulting full frame to a projection screen or other viewing medium.
- Electrodes are nominally transparent, and indeed are not readily visible in displays of modest size, such as for instance less than five feet along a diagonal .
- Liquid-crystal light valves are to be carefully distinguished from the liquid-crystal display or device modulators discussed just above. Whereas an LCD operates in transmission and requires passing the projection beam through electrodes in the image-writing (input) stage of the modulator, an LCLV operates in reflection and has entirely separate image- writing and projection stages.
- the image-writing stage may have electrodes, or may be written optically or thermally, but all such activity is entirely isolated from the projection stage by an opaque mirror. There is one, unitary electrode in the projection stage but its edges are ordinarily outside the image frame.
- LCLV may be a twisted-nematic type, a birefringent type, a hybrid of the two, etc.
- an LCLV structure and operation of an LCLV —
- an input or writing stage first develops a voltage that varies spatially within the device frame, in accordance with brightness variations that constitute an image to be projected.
- An output or reading stage has a polarization-influencing characteristic — such as a particular index of refraction, corresponding to a particular optical phase delay.
- the writing stage and reading stage are separated by an opaque mirror, and the whole assemblage is sandwiched between two transparent planar electrodes. By virtue of these electrodes, voltages developed in the writing stage are applied to the reading stage.
- the spatially varying voltage induces corresponding spatial variations in the polarization-influencing characteristic of the reading stage. Meanwhile polarized light — the reading beam — is introduced into the output or reading stage, reflected from the internal mirror and returned toward the projection screen.
- the spatial variation in index causes the desired image-brightness variations to be expressed as a spatially varying polarization field, carried by the light beam leaving the reading stage.
- this polarization field is decoded or developed by a polarization analyzer so that the beam carries a spatially varying intensity field, which is perceptible to the eye as an image.
- this strategy is replicated for each of three primary colors .
- the resulting beam or beams are projected (with or without combination into a common projection beam) in a substantially conventional way through a projection lens to a viewing medium.
- the writing stage may be excited with very low-intensity light as for instance from a small CRT (or by low voltages applied to an electrode matrix, or in other ways)
- the reading stage is preferably excited with extremely intense, projection-level illumination — such as, in the Hughes work, a high-current arc lamp.
- extremely intense, projection-level illumination such as, in the Hughes work, a high-current arc lamp.
- LCLVs with, exclusively, such incandescent sources ("white" light) .
- One reference does propose the use of LCLVs with laser sources — and that is not a Hughes docu- ment but rather is the above-noted patent of Minich (Prox- ima) . Both types of usage are discussed below.
- the discarded chordal areas 775 amount to about thirty-six percent of the area of the circle — as is verified by simple arithmetic later in this document. Thus 36% of the energy in a circular beam is wasted in masking to a square frame.
- a perceptible glow may pass through an LCLV to the projection medium in regions that should (based on the written image) be dead black.
- some of the costly optical energy extracted from the omnidirectional source — and still remaining after the several inefficient processes discussed above — is used to illuminate areas that are dark in the desired image.
- Henderson teaches simply shaping of a white-light beam, from an incandescent source, into a shallow slot-shaped beam — and scanning that beam across an LCLV modulator. In this case, since the light source itself is continuously operating, a continuous sweep produces a continuum of overlapping successive beam positions rather than a discrete-stepping effect. Henderson's goal is to greatly improve energy uniformity, masking, read/write efficiency and contrast of an LCLV system by placing the reading light in precisely the region where the writing is taking place.
- a telecentric optical system is defined in the Gold patent as a system in which all "chief rays" are made to parallel the optical axis of the system.
- a chief ray is by definition a ray that originates at an off-axis point of an object or source and crosses the axis.
- these are characteristics of conventional white-light systems in which, for example, rays from various points of an object which extends transverse to the axis are collected in a lens and redirected — many typically crossing the axis — to construct an image also transverse to the axis (but located at another point along the axis) .
- Schmidt proposes resolving the Henderson problems through particular forms of rotating polygonal deflectors that are transparent, and ingeniously configured to preserve telecentricity.
- Gold teaches use of a more conventional reflective rotating polygon, but coupled with somewhat elaborate optical elements to pre- and postcondition the slot-shaped beam for deflection at the polygon — also to preserve (or restore) telecentricity.
- Minich proposes to use LCLVs with laser sources — including red laser lines in the neighborhood of 620 nm.
- Minich asserts that his LCLV-based apparatus is "substantially similar . . . to the system [using a transmissive LCD modulator] , except that the [LCLV] apparatus operates reflectively rather than transmissively.
- trans- missive LCD devices are objectionable for very-large-format projection because of conspicuous electrode patterns which they display.
- Minich Neither the problems of beam-shape matching and contrast nor the possibilities of scanning slot-shaped beams are taken up by Minich — in either his above-noted patent or his more-recent one, U. S. 5,700,076. These problems are just as important with laser sources as with the Hughes white lamps.
- Minich furthermore fails to address the desirability of infinite sharpness, although this represents a major application for laser projectors.
- the conventional understanding is that the image-forming mechanisms of LCLV modulators destroy laser-beam coherence and thereby foreclose achievement of infinite sharpness.
- Minich says nothing of the problems of brightness uniformity. Whereas beam nonuniformity in white-light LCLV systems is significant, in a laser-beam LCLV system it is of the utmost importance — because laser beams are subject to a number of artifacts that become plainly visible on the projection screen if a laser beam is simply expanded to flood an LCLV reading stage.
- Minich refers to documents of Texas Instruments Incorporated (col- umn 5, line 58) and of Hughes (column 9, line 58) .
- the overall focus of the Proxima development program, as suggested in the Minich patent, is upon very compact, lightweight and inexpensive projectors that are very unlike the very large, high-quality Hughes product (and two orders of magnitude lower in price) .
- Actual Proxima machines on the market appear to correspond to the more-recently issued '076 Minich patent mentioned above, not to anything in Minich '263.
- the present invention introduces such refinement.
- the invention has several independently usable facets or aspects, which will now be introduced. Although these aspects are capable of use independently of one another — and as will be seen they have distinct advantages considered individually — for optimum enjoyment of their benefits the various aspects are preferably practiced together in conjunction with one another, and most preferably are all practiced together.
- the invention is a laser projector which includes laser apparatus for projecting a picture beam that includes visible laser light.
- the light is of wavelength about six hundred thirty-five nanometers (635 nm) or longer.
- a reflective liquid-crystal light valve for modulating the beam with a desired image.
- my invention uses a liquid-crystal light valve in conjunction with a laser operating wavelength region that runs counter to all the conventional wisdoms discussed in the background section of this document.
- my invention provides — and is the first to provide — a laser projector that makes an energy-efficient, bright, rapid-motion image with rich, full colors that are equal to or better than the gamut and saturation produced by conventional motion-picture film projectors.
- the wavelength region of choice has been about 610 nm — and AOM systems are wholly unsatisfactory for the reasons described earlier (inefficient use of light energy, low moving-image bandwidth, and complex optics) .
- 610 nm red yields exciting, snappy, punchy colors. Actually, however, 610 nm corresponds to orange, or at most a red-orange, and this choice prevents attainment of rich color. The rose colors, deep reds and purples, and even a good honey color are difficult to achieve if the red is not deeper. This is the reason that red roses appear a banal orange-ish on television.
- the apparatus project a beam of wavelength between about 635 and 650 nm.
- the most highly preferred wavelength is about 647 nm.
- a projector according .to this aspect of the invention also provide green and blue laser light — for mixing with the laser light of wavelength about 635 nm or longer to provide substantially pure neutral colors including pure white and pure black. (Naturally the green and blue are also used for other purposes.)
- black is an absence of all light and color. It may be hard to conceive how con- trolling spectral content of light used in an image-forming device can influence what is seen when all light is absent. Since the era of oil paintings and throughout the age of color photography and color lithography, however, achieving accurate color balance "in the shadows" has been a mark of particular excellence. Precise control of color in this difficult region is an important figure of merit. Thus what is really at issue is the capability of a color-reproduction system to represent dark neutral colors , colors along the neutral axis of the color-gamut solid, in the limit as the black pole is approached.
- the laser apparatus projects substantially cyan light with the blue or green light, or both.
- cyan has been systematically removed from laser beams for image-projection use, thereby both discarding a large fraction of the light power in the beam and making the achievement of good whites and blacks more awkward.
- my present invention accordingly a very significant increase in available beam power is enjoyed, while at the same time color mixing is enhanced — not only along the neutral axis or at the surface of the color-gamut solid, but throughout — merely by refraining from exclusion of naturally occurring cyan lines.
- this aspect of my invention preferably also includes some means for at least partly suppressing visible speckle in such a picture.
- the suppressing means preferably include apparatus for displacing the beam during its projection, in conjunction with the light of wavelength about 635 nm or longer. I have discovered that this color is particularly beneficial in reducing or eliminating speckle, when used together with at least certain arrangements for beam displacement.
- apparatus of this first aspect of my invention also be able to receiving high-bandwidth red, green and blue computer-monitor signals from a computer; and that the projector thus serve as a high-color-fidelity computer monitor.
- the liquid-crystal valve is not controlled by light derived from traditional or conventional broadcast video signals.
- the liquid-crystal light valve is preferably controlled by light or control signals applied to the valve by writing onto a control stage of the valve:
- the light valve is controlled by light substantially derived from a type of conventional or traditional broadcast video signals.
- substantially no color correction or gamma adjustment be applied to remove the effects of using the 635 nm or longer-wavelength laser light instead of broadcast video standard red.
- Every laser in the apparatus is exclusively a solid-state laser.
- every laser in the apparatus is instead exclusively a gas laser.
- my invention is a laser projector that includes laser apparatus for projecting a picture beam along a path.
- the beam includes laser light which tends to generate visible speckle when used to form a picture on a projection medium.
- the projector includes some means for at least partly suppressing visible speckle in such a picture.
- some means for at least partly suppressing visible speckle in such a picture For purposes of generality and breadth in describing and discussing my invention, I shall refer to these means simply as the "suppressing means".
- the suppressing means in turn include some means for displacing the path during projection of the beam. Again for generality I shall call these means simply the "displacing means" .
- this aspect of my invention reduces speckle without the primary drawback of prior systems — namely, absorbing or diffusing the beam.
- This second facet of my invention thereby gains not only a significant advantage in the efficient use of optical energy but also substantially preserves a sort of collimation or pseudo- collimation, which as will be seen has major advantages of its own.
- the projector further include a liquid-crystal light valve having a beam-modulation stage for impressing an image onto the beam; and that the displacing means scan the beam over this beam-modulation stage during projection.
- the displacing means scan the beam over the beam-modulation stage by mechanically or electrooptically deflecting the beam path rotationally.
- the directing means com- prise an optical deflecting element mounted for mechanical rotation.
- the deflecting element comprises a mirror mounted on a galvanometer or motor (such as for example a stepping motor) .
- a galvanometer or motor such as for example a stepping motor
- the mirror be mounted for rotation about an axis substantially in a reflective surface of the mirror.
- the projector also include some means for writing an image incrementally onto successive portions of the control stage; and some means for controlling the displacing means in a special way.
- the controlling means operate to direct the beam onto successive selected portions of the modulation stage, and to generally synchronize the beam with the image-writing means.
- the controlling means provide the beam displacement needed for reduction or elimination of speckle — but yet their small cost and slight added complexity need not be charged off to the achievement of speckle suppression alone, since stepping a shallow beam, and synchronizing the beam with the image-writing process, has numerous other important advantages .
- control stage be a photosensitive stage that receives an incrementally written optical image.
- control stage includes an electrode matrix that receives incrementally written electrical voltages.
- the deflecting means be substantially nondiffusing. Incorporation of such deflecting means, in the writing and controlling means discussed above, produces a remarkable benefit: the projector can be used in forming a speckle-suppressed image on an irregular projection medium that has portions at distinctly different distances from the projector. In other words, the projector has speckle suppression in conjunction with the previously discussed capability of infinite sharpness.
- the liquid-crystal light valve operates by introducing at least partial disruption of the laser-light coherence.
- This second aspect of my invention nevertheless preferably includes some means for projecting the picture beam onto such an irregular projection medium.
- the picture beam forms an image that appears substantially sharp on the portions of distinctly different distances — notwithstanding the at least partial disruption of coherence. This extraordinary result is entirely inconsistent with the conventional understandings in the art.
- noncrossing rays which may be called pseudocollimation or perhaps quasi collimation — still further in turn, is maintained by the nondiffusing mirror or other deflecting optics in the speckle-suppression aspects and embodiments of my invention . Since the rays neither cross as in a focal system nor become scrambled as in a diffuser, there is no crosstalk between different portions of the image — or in other words spatial modula- tion is preserved.
- the displacing means be substantially lossless, to within one percent of beam intensity.
- the projector also include beam-expansion means which cooperate with the dis- placing means to achieve a net gain in light-energy efficiency.
- the displacing means and beam-expansion means cooperate to substantially eliminate initial nonuni- formity of brightness in the beam.
- the beam-expansion means may take the form of, for example, entrance optics ahead of the displacing means; these optics advantageously expand the initial laser beam to an optimum specialized shape for displacement by the displacing means.
- the laser apparatus include optical means for shaping the picture beam to a shallow cross-section; and that the displacing means also shift the picture beam on the projection medium, during projection.
- the optical means preferably take the form of plural lenses in series for adjusting the beam dimension in two substantially perpendicular directions, or a curved mirror that forms part of the displacing means.
- a curved mirror it advantageously shapes the picture beam to a shallow cross-section.
- it is mounted in a galvanometer movement, or mounted to a motor (or otherwise equivalently mounted and driven in controlled oscillation) , to scan the shaped beam over the modulation stage.
- a laser projector that includes laser apparatus for projecting a picture beam which in turn includes exclusively laser light.
- the projector also incorporates a liquid-crystal light valve having a beam-modulation stage for impressing an image onto the exclusively laser-light beam, and having a control stage, distinct from the beam-modulation stage, to control the "impressing" function.
- the projector includes some means for writing an image incrementally onto successive generally slot-shaped portions of the control stage — as before, called the “writing means” or “incremental writing means”.
- the projector also has some means for directing the exclusively laser-light beam onto successive selected generally slot-shaped portions of the modulation stage, and for generally synchronizing the exclusively laser-light beam with the image-writing means — i . e. , "directing and synchronizing means” .
- the laser apparatus initially projects the exclusively laser-light picture beam having substantially all rays substantially parallel to a common optical axis, with substantially no ray crossing the optical axis or otherwise passing through the center of any aperture stop.
- My preferred apparatus therefore has no telecentric zone.
- the exclusively laser-light picture beam is not focused at or near the directing means or the modulation . stage, or elsewhere within the laser projector.
- the liquid-crystal light valve includes a substantially distinct spatial portion for modulation of each distinct spatial portion of the exclusively laser-light beam, respectively — a condition that cannot be achieved with any of the Henderson, Schmidt or Gold arc-lamp-based inventions.
- the projected beam has a cross- section that is substantially uniform in intensity, rather than having a Gaussian intensity distribution (as Gold states is present for at least the vertical dimension of the slot) . I say “substantially” for reasons that will later become clear in conjunction with discussion of Figs. 25a and 29.
- substantially the entire cross-section of the exclusively laser-light beam, with only negligible masking (preferably at two very extreme edges only) be directed onto the successive selected portions of the modulation stage.
- substantially each control-stage portion have a substantially corresponding modulation-stage portion; and in this case that the directing-and-synchronizing means generally synchronize selection of modulation-stage portions with writing at corresponding successive control-stage portions, subject to a delay generally equal to rise time in the modulation stage.
- the directing means comprise an optical deflecting element mounted for rotation.
- the deflecting element comprises a mirror mounted on a rotating disc, or multiple mirrors mounted about a rotating disc.
- the directing means include a mechanically rotated reflective or refractive element; and that all dimensions of the exclusively laser-light beam at the light valve be substantially unaffected by dispersion in the directing means, regardless of whether the element is reflective or refractive — not possible with light from a halide lamp, filament lamp, arc lamp or other fundamentally incandescent source.
- control stage is a photosensitive stage that receives an incrementally written optical image.
- the projector includes some means for reflecting the beam from the directing means into the beam-modulation stage and for transmitting the beam, after return from the beam-modulation stage, to form a picture on a projection medium.
- the laser apparatus be generally disposed on a first level — while the light valve, writing means, and reflecting-and- transmitting means are generally disposed on a second level above or below the first level .
- the directing means also transfer the beam from the first level to the second level .
- the directing means do double duty as means for effecting the needed transfer. More specifically, in this arrangement preferably the directing means turn the beam from a path generally associated with the first level to propagate in a direction generally perpendicular to that path, toward the second level .
- the beam follow a first, generally rectilinear path from a laser source to the directing means; and then follow a second, generally recti- linear path from the directing means toward the beam-modulation stage. It is further preferable that the directing means also turn the beam from the first path into the second path, thus achieving greatly improved simplicity in layout, a minimum number of lossy optical elements, and efficiency of use of the several components.
- the first and second paths are generally mutually perpendicular.
- my invention is a laser projec- tor that includes laser apparatus for forming a picture beam that includes laser light.
- the laser apparatus produces an initially substantially circular laser-light beam subject to nonuniform illumination.
- the projector also includes some means for transmitting a beam out of the projector for viewing by an audience as images on a substantially rectangular viewing screen. These means may be called, for reasons as above, the "transmitting means" .
- image-forming means operate by using the circular laser-light beam without masking off significant fractions of the laser-light beam.
- the image-forming means include:
- this aspect of my invention substantially eliminates masking losses, by fitting essentially all the energy from the entire circular laser beam to a rectangular image format. This is accomplished by forming the reshaped beam that generally matches the width of the rectangular image — and then sweeping this reshaped beam through successive overlapping positions along the height of the image, so that the aggregate of the continuum of overlapping shallow beams matches the overall height.
- the fourth major aspect of my invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits I prefer to practice my invention with certain additional features or characteristics.
- the projector further include some means for minimizing the influence of nonuniformity of illumination in the initially substantially circular laser- light beam.
- these minimizing means include the reshaping and scanning means, which operate in such a way as to tend to cause the nonuniformity to average out. More specifically, the reshaping means typically introduce additional illumination nonuniformity along the width of the shallow, wide laser-light beam; and I prefer that the image-forming means further comprise means for compensating for the addi- tional illumination nonuniformity.
- my invention is a laser projection system for forming an image on an irregular projection medium having portions at distinctly differing distances from the projector.
- the system includes laser apparatus for projecting a picture beam that includes laser light.
- It also includes a liquid-crystal light valve for impressing an image onto the beam; and some means for pro- jecting the beam from the light valve, with the impressed image, onto the irregular projection medium.
- this aspect of my invention is the first system of any raster type that forms a sharp image on a pro- jection medium of the kind described.
- the only disclosed laser projector using a liquid-crystal light valve is the previously discussed Minich patent 5,517,263 — and that patent teaches nothing of imaging on such a projection medium. That omission should be of little surprise, in view of the previously mentioned belief among at least some experts in liquid-crystal light valve theory. As noted earlier, that belief is to the effect that such a light valve is incapable of the needed "infinite sharpness" characteristic that would enable projection on irregular projection media as defined in the above description of the fifth facet of y invention.
- the irregular projection medium be one of these :
- the fifth aspect of my invention as very broadly conceived, and as set forth above, is for use with an irregular projection medium of the character described. That is to say, the irregular projection medium is simply a part of the context or environment of the invention.
- That system is in effect a combination of the laser projector of the fifth aspect of the invention with the structures of the variegated types discussed.
- this particular preferred form of my invention enables presentations of an extraordinary and outstanding character.
- this form of my invention can be used to create outdoor public spectaculars in which literally many hundreds of thousands of people view giant images projected with sharp clarity upon massive surfaces.
- the surfaces may be selected large buildings — whether skyscrapers, huge domes , statues or monuments — or a natural canyon such as for instance the walls of Yosemite Valley or even the Grand Canyon .
- My invention is capable of throws on the order of kilometers, still maintaining infinite sharpness, and (with very large powerful lasers or ganged multiple lasers) image dimensions the size of a football field.
- the images are not limited to vector graphics as in primitive laser shows, but can be raster images including scenery, natural faces, action scenes and anything else that can be made into a bitmap sequence or otherwise displayable image.
- this form of the invention can create, for extremely large audiences, special shows on the interiors of large domes or other large irregular spaces such as the various inside walls of a very large train station, opera house, or stadium (including parts of the audience in the stadium) .
- liquid-crystal light valve operates by partial disruption of laser-light coherence in the beam; and I prefer, notwithstanding the partial disruption of coherence, that the image appear sharp on the projection- medium portions of differing distances. I also prefer that the image appear substantially evenly illuminated, except possibly where light is distributed over a receding surface.
- my invention is a laser projector that includes a light source for forming a picture beam — and a modulator for impressing a latent image onto the picture beam. It also includes a polarization analyzing cube for receiving light from the modulator and developing the image.
- This facet of the invention also includes some means for projecting the beam, with the developed image, for viewing by an audience. As before I shall refer to these means as the "projecting means”.
- the foregoing may represent a description of definition of the sixth aspect or facet of my invention in its broadest or most general form. Even as couched in these broad terms, however, it can be seen that this facet of the invention importantly advances the art.
- the use of an analyzing cube rather than a polarizing-sheet-material analyzer or a dichroic analyzer is advantageous because the polarization selectivity of a cube analyzer is much sharper than that of the other types. Accordingly with this sixth facet of my invention the resul- tant image contrast and resolution are superior to those available heretofore.
- the cube also supply the picture beam to the. modulator.
- the light source comprises a laser, which — among the many benefits discussed earlier — enhances the sharpness of polarization sensitivity, since the cube can be one particularly designed for operation in a very narrow spectral band about the laser lines.
- antireflective coatings be formed on three cube faces through which the beam passes to and from the modulator.
- the cube has six faces, including three through which the beam passes to and from the modulator and three others; and light absorbers are at one or more of the other faces .
- Fig. 1 is an isometric drawing — rather schematic and not to scale — of a laser-projector optical system according to a preferred embodiment of the present invention, using gas lasers or alternatively solid-state lasers, or both;
- Fig. 2 is a plan view of the upper level of the Fig. 1 embodiment, still not to scale but somewhat more realistic than Fig. 1 as to proportions;
- Fig. 3 is a like view of the lower level of the same embodiment, but showing a variant optical train
- Fig. 4 is a left-side elevation, like Fig. 2 as to accuracy of relative dimensions, of the same embodiment;
- Fig. 4a is a face-on elevation of a liquid-crystal light valve as used in the embodiment of Figs . 1 through 4 ;
- Fig. 5 is an isometric drawing, conceptual and not to scale, for a preferred embodiment of the invention related to Fig. 1 and enlarged to show only the beam-scanning por- tion for one color channel (e. g. red) , using partly reflective and partly refractive beam shaping — and showing the scanning system at the top of its range;
- one color channel e. g. red
- Fig. 6 is a like view but showing the scanning system at a different stage in the scanning operation, namely at the center;
- Fig. 7 is a like view with the scanning system at yet another stage, namely the bottom;
- Fig. 8 is an elevational optic diagram, showing the optical path at the rotationally oscillating mirror of the Fig. 1 through 6 systems unfolded — i . e. , representing the mirror only as a straight dashed line;
- Fig. 9 is a plan view corresponding to Fig. 8.
- Fig. 10 is a variant mirror that is curved in two orthogonal directions, to replace the mirror and two lenses in Figs. 1 through 9;
- Fig. 11 is an elevational view like Fig. 8, but using the Fig. 10 rotating mirror in a variant primarily reflective beam shaper (but still with at least one recollimating lens at the modulator section of the system) ;
- Fig. 12 is a plan view corresponding to Fig. 11;
- Fig. 13 is a view like the upper portions of Figs. 5 through 7 but showing a stationary mirror and a nonmechani- cal beam deflector;
- Fig. 14 is a chromaticity diagram (after Judd and Wys- zecki , Color in Business, Science and Industry, Second Edition, Wiley 1952, 1963) showing the wavelengths and chromaticity positions of visible light wavelengths;
- Fig. 15 is a conceptual system diagram showing the CRT- driven Fig. 1 embodiment in block-diagrammatic form
- Fig. 16 is a like view of a related embodiment operating from input-image information applied directly by sweeping amplitude-modulated laser-diode illumination two-di- mensionally across the control stage of a liquid-crystal light valve, rather than through CRT means;
- Fig. 17 is a like diagram showing a preferred embodiment operating from input-image information applied directly by illuminating the control stage of a liquid-crystal light valve with images from a small transmissive liquid-crystal display modulator;
- Fig. 18 is a diagram like Fig. 15 or 16 but showing a. different preferred embodiment operating from noninterlaced input-image information such as a vector, bitmap or other computer file scanned from an image or generated in a com- puter, and written electronically to the control stage of a liquid-crystal light valve;
- Fig. 19 is a like diagram showing still another preferred embodiment operating from input-image information in the form of a nonincrementally written still image
- Fig. 20 is a like diagram showing yet another preferred embodiment using input-image information in the form of nonincrementally written motion-picture film color separations
- Fig. 21 is a like diagram showing yet another embodiment using input-image information in the form of live images acquired and written without electronics, optically, to the light valve — and also projected — all in real time with no need for storage;
- Fig. 22 is a timing diagram showing synchronization in the Fig. 19 embodiments, particularly with delay to accommodate rise time in a liquid-crystal display;
- Fig. 23 is a simplified optical diagram showing two cooperating principles of operation of a speckle-suppression system that is incorporated into certain preferred embodi- ments of the invention — particularly with the system in one stage of its operation;
- Fig. 24 is a like view showing the same system in another stage of its operation
- Fig. 25 is a diagram showing some representative dis- tributions of illumination across a laser beam cross-section, for comparison with an idealized distribution also shown;
- Fig. 25a is a like diagram showing very schematically or conceptually another representative laser-beam intensity distribution, which I prefer to use with preferred embodiments of my invention.
- Fig. 26 is a diagram showing needed masking for a prior-art system using a circular light beam and a square projection screen
- Fig. 27 is a like diagram for a screen with 4:3 aspect ratio
- Fig. 28 is a like diagram for a screen with 16:9 aspect ratio
- Fig. 29 is a group of coordinated diagrams, the first showing in elevation an intensity distribution related to that of Fig. 25a, still very conceptually, and also conceptually showing conspicuous irregular intensity nonuniformi- ties such as are typically found in a laser beam if used in a polarization-driven light valve; and the remaining diagrams showing the shape relationship between an original circular laser light beam and a very shallow reshaped beam for scanning over a projection screen, in the efficiency- and uniformity-increasing system of the present invention; and also showing the illumination distribution in the reshaped beam, and showing residual correction factors that can be required or desirable (or superfluous) in both cases;
- Fig. 30 is a group of very simplified coordinated diagrams (a side elevation at top right, plan at bottom right, and viewer's perspective at left) showing in a somewhat fanciful way the imaging capabilities of a system according to the invention as used with an irregular projection medium comprising the exteriors of various buildings or other structures including a dome, in accordance with the invention, and particularly relative to disrupted coherence;
- Fig. 31 is a like set of diagrams (side elevation at top, plan at bottom) for another type of irregular projection medium that comprises the interior of a dome;
- Fig. 32 is a thumbnail sketch that is a like view but even more fanciful and with another type of irregular projection medium that includes a waterfall or fountain, or both ;
- Fig. 33 is a like view with another type of irregular projection medium including plural scrims behind a theater proscenium;
- Fig. 34 is a like view with yet another type of irregular projection medium comprising foliage.
- Fig. 35 is a like view with still another type of irregular projection medium comprising arbitrary assemblages of discrete articles, including creatures.
- Laser-projector apparatus is advantageously laid out in two levels or tiers, one above the other. Either level can be used for the sources 10 (Figs. 1-4), and the other for the modulation and projection subsystems 23-44, but I prefer to put the sources on top. This configuration is particularly beneficial in allowing very easy exchange of the lasers , for use in image shows calling for higher- or lower- power beams . Such interchange often demands a change of projection lens 44, too. The lens, however, is generally well forward of the lasers and therefore accessible regardless of the level on which it is mounted.
- the blue and green beam llgb is split at a dichroic separator 12gb to form respective beams of green 13g and blue 13b, which traverse plane mirrors 14, 16 to reach their negative lenses 18g, 18b.
- the two-mirror dogleg path 13g- 15g-17g is not strictly necessary but only included for convenience and to facilitate placement of the lasers more compactly forward above the modulation stages. Transfer of the laser beams from the upper level to the lower — together with a change of direction that is needed for entry of the laser beams into the modulation subsystem at right angles to the final projection path — is accom- pushed by small folding mirrors 20 that also serve in speckle suppression, circular-to-rectangular beam shaping, and brightness and contrast enhancement.
- planar mirrors 20 are preceded by respective negative lenses 18 and cylindrical lenses 19, and are mount- ed to drivers 21 for a small angular oscillatory rotation.
- Each driver is preferably a galvanometer movement but may instead be a motor, stepping motor, solenoid driver, piezoelement, pneumatically driven reed, or other suitable equivalent.
- beam deflection alternatively may be accomplished with spinning polygon mirrors or other known devices.
- the argon laser lOgb can instead be shifted to a position in line with the multipurpose planar folding mirror 20g in the green channel. That mirror with its entrance optics 18g, 19g is then reversed in orientation, and the angles of the separator 12gb and deflector 14b adjusted to compensate.
- the beams from the mirrors proceed through lenses 23 into the entry faces 24 of polarizer-analyzer cubes 25.
- Each cube is made of two forty-five-degree right prisms, one of which has a polarizing dichroic layer 26 coated on its hypotenuse — i . e. , at the interface of the two prisms.
- such a cube provides relatively very sharp polarization discrimination, and thereby improved image contrast and sharpness relative to Polaroid® material or stand-alone dichroic polarizers.
- this function is not operative with regard to the beam entering downward through a top entry face 24. Because the polarization of our laser beams is typically even sharper than the discrimination capability of the cube, ordinarily the central polarizing layer 26 instead has substantially no effect on the polarization state at this point.
- the polarizing layer therefore simply deflects the downward-incoming beam at ninety degrees and out through the rear face 27 into the front or reading stage of the liquid- crystal light valve modulator 30.
- the rear stage of each modulator 30 is written by an input image that is coupled through a fiber-optic or preferably lens-system matcher 31 from a respective infrared cathode-ray tube 32.
- the image signal for the CRT 32 is provided through cables 33 from a conventional source — either computer video or conventional broadcast video, or virtually any other source if the system is suitably configured for the corresponding form of data.
- the liquid-crystal light valve 30 may be substantially conventional , or of a type not yet known . As mentioned earlier, several variant kinds of these valves have been described and are available. Each valve has a rectangular image frame (Fig. 4a) .
- the function of the valve 30 includes receiving a consistently polarized picture beam or reading beam from the rear, output face 27 of its cube 25, and reflecting the beam at an internal mirror within the valve.
- the valve thereby returns the reading beam forward into the face 27 from which it came.
- the valve introduces into the reading beam a variable delay — and therefore variable polarization state — which correspond at each point in the frame to writing-light intensity, modulation-voltage level, or other type of control stimulus in the control or writing stage of the valve 30.
- the beam reentering the cube face 27 thus has read, or has had impressed upon it, a latent image expressed in polarization state.
- the polarization state at each point in the image frame can be described as a rotation that is related to the intensity of the writing image (or control voltage etc.) at the corresponding point.
- the beam Upon reaching the analyzing layer 26 within the cube, the beam is in effect decoded: light polarized in the original polarization plane is deflected back up, generally toward the multipurpose mirror 20, and thus discarded — while any light polarized at ninety degrees to the original plane passes through the dichroic layer and out the forward face 35 of the cube and into the projection subsystem proper.
- the latent image 34 component of each primary color is thus developed and forwarded for projection.
- the three primary image components 34r, 34g, 34b are next combined by a turning mirror 37r and dichroic filters 39gb, 41gb to form a unitary full-color image beam 43.
- a projection lens 44 controllably expands — but does not focus — this optical signal to provide an expanding beam 45 for propagation to a projection medium.
- the lasers include a red source lOr in the form of a krypton-gas laser, most preferably emitting red light in the 647 nm region. While this is the ideal, I prefer to use laser spectral lines that are between 635 and 650 nm, or at least are above 635 nm; these are far superior to the 610 nm conventional preference, or the approximately 620 nm indicated in the Minich patent for use with liquid-crystal modulator types.
- Wavelengths at 647 or at least above 635 nm are capable of forming rich colors on the projection medium, equal or favorably comparable with those of projected images from film — which as noted earlier is the appropriate standard of comparison for the image quality produced by my invention.
- Deep red roses, deep red football uniforms, deep red sunsets , and vivid purples as seen using my invention are actually deep red and purple, not merely the gaudy orange or red-orange seen with 610 nm systems.
- a green and blue source lOgb is also included in my apparatus. This is preferably implemented as an argon-gas laser emitting green and blue light in the regions below roughly 540 and 490 nm respectively.
- All three wavelength regions are in essence chosen for their capability to provide well-saturated colors not only when appearing in pure form but also when mixed; and the relative intensities mentioned earlier are preferred for the capability to mix to good neutral whites, grays and blacks when needed.
- the ability to yield good saturation relates to the positions of these particular wavelengths along edges and very near the corners of the familiar chromaticity diagram (Fig. 14) .
- Beam-shaping and steering Preferred forms of the invention provide one or more optical components that reform the round-cross-section laser beam into a wide, shallow slot-shaped beam (for several different beneficial uses , as described in subsection "e” below) , and turn that beam from the source tier of the apparatus downward into the modulation subsystem.
- These shaping and steering functions may be accomplished with various sorts of devices:
- This first lens causes the exiting beam to slightly expand (Figs. 5-7), in all transverse directions, while propagating. It is helpful to consider this process in only the vertical plane (Fig. 8, in which the dashed line 20 repre- sents the planar folding mirror 20, and the optical path is shown unfolded) .
- the vertical expansion is at such a rate that, upon reaching its cube 25 and modulator 30, the height of the beam 51, 53, 54 will correspond to several raster lines 55-57 of the input image — or in any event a region tall enough to encompass the height of the persistence zone 59 of the writing mechanism 58.
- the negative lens 18 causes the beam to follow an envelope that expands symmetrically (i . e. , not anamorphically) , so that all the previously collimated rays now progressively and slightly separate from one another.
- the speed of this expansion is determined so as to satisfy the stated height criterion at the modulator.
- a circularly cylindrical lens 19 while leaving the vertical expansion substantially undisturbed, superim- poses an additional somewhat steeper horizontal expansion, best seen in the horizontal plane (Fig. 9) .
- This expansion, as well as the resulting composite effect of the two lenses 18, 19, is of course distinctly anamorphic.
- the circular- cylindrical optic is selected to provide just enough hori- zontal expansion that — again upon reaching the cube and modulator — the width of the beam 51, 53, 54 will substantially just very slightly overfill the frame width EE (Fig. 4a) of the liquid-crystal valve.
- the two elements 18, 19 thus complete the reformation of the beam into a wide and shallow shape that has been specifically optimized for the processes that follow.
- the small planar mirror 20 then turns the reformed beam (still expanding anamorphically as it proceeds) downward 22.
- the two lenses 18, 19 constitute the previously mentioned beam-expanding means.
- rays in the beam while separating from one another do not cross one another or become scrambled, and thus may be described as pseudocollimated.
- the mirror 20 not only turns the beam but also oscillates 20' rotationally 5 about a horizontal axis, and so sweeps the beam 22 forward and back over the recollimator 23 and over the entry face of the cube 25. After reflection at the polarizer/analyzer layer 26, so that the beam is again propagating horizontally, this back-and-forth displacement of the beam path
- the beam is continuously shifted or successively stepped without overlap from positions 54t (Fig. 5) at top of the image frame, through positions 54c (Fig. 6) at
- the wide, shallow slot-shaped projection beam 45 sweeps from topmost through central to bottommost positions 46t, 46c, 46b on the projection medium 47.
- the slot-shaped beam that results does have significant nonuniformity of brightness along its length (i . e. , from side to side along the horizontal extent of the beam) .
- mity can be corrected by substituting a differently shaped optic — for instance perhaps an elliptically or hyperboli- cally cylindrical lens , or possibly an entirely custom- designed shape — in place of the circular cylinder 18.
- a differently shaped optic for instance perhaps an elliptically or hyperboli- cally cylindrical lens , or possibly an entirely custom- designed shape — in place of the circular cylinder 18.
- This optic is a curved astigmatic or anamorphic mirror having one relatively more weak or gradual curvature 120e about a generally horizontal axis, and another sharp curva- ture 120d about a generally vertical axis.
- This mirror might advantageously be cast, for example in epoxy, and then silvered.
- this mirror would spread the beam 122 gradually (Fig. 11) in the vertical plane and more steeply (Fig. 12) in the horizontal.
- the single mirror 120 would thereby yield an output beam 122 with a shallow elongated output cross-section 151 — similar to the beam 22 in the prototype system.
- the shape should not only spread the circular input beam 11 anamorphically as with the two lenses discussed above, but also should trim the distribution of the rays to at least approximately equalize intensity along the length of the shallow, elongated beam. Possibly such an optic may introduce aberrations of shape that require compensation in the recollimator 123.
- the mirror 120' is to be mounted for oscillatory rotation 120' , very generally as described above for its planar counterpart 20. With a curved mirror, care must be exercised in positioning the rotational axis relative to the mirror shape, to minimize undesired small effects on beam direction or movement at the modulator. Some small movements, as noted earlier, are beneficial.
- Still another solution to the shaping and steering functions is an elec- trically, magnetically or piezoelectrically controlled cell 61 (Fig. 13) in conjunction with a mirror 20, 120 that is fixed rather than oscillating.
- the mirror may be planar, necessitating additional optics similar to the previously discussed lenses 18, 19; or may be specially formed (Figs. 10-12) .
- Various control devices such as Pockels or Kerr cells. may be usable for such a system. Typically the performance of these devices is strongly wavelength dependent; however, this characteristic once again represents little or no obstacle since laser beams are more nearly monochromatic than arc lamps and like broadband spectral sources .
- Nonmechanical sweep systems such as introduced here may therefore prove superior for at least some applications.
- the line doubler performs very useful functions, particularly important when using conventional broadcast video signals: (1) separating 62 the color chan- nels to isolate the red, green and blue image components, and (2) interpolating additional raster lines between the lines of the original image data, and (3) providing a reformatted all-digital output 63 to each CRT.
- the device also provides a so-called "image-enhancement" function for any video f ed. Interpolation is important because many conventional . signal formats provide a relatively coarse raster spacing that is conspicuous and distracting when greatly enlarged. In the context of my invention the original coarse raster would be particularly objectionable because it is more pronounced when formed by a sharp, high-contrast laser projector.
- the line doubler can accept a variety of input-signal formats, including various conventional broadcast signals and computer-style video data.
- the doubler also incorporates convenient features such as facilitating audio management.
- the doubler directs each reformatted image-data set 63 to the corresponding CRT 32 in the form of an amplitude- modulated data stream 33, synchronized with two-dimensional sweep signals 64 that control the vertical and horizontal position of the CRT electron beam.
- These sweep signals 64 are also synchronized 65 with one-dimensional sweep of the high-power laser beam 11, 22 (Fig. 15) by the oscillating mirror 20.
- Each CRT optical output (or output coupler) 31 writes the image to the corresponding modulator 30, which simultaneously receives the swept beam 22 and produces a high-power output beam 34 for combination and projection 44 as a uni- tary beam 45 to a projection medium 47.
- the light pipe must be made with extremely fine fibers for applications involving very large projection screens, to avoid image granularity (in effect a type of pixel structure) under the associated conditions of very high enlargement.
- a conventional lens arrangement is used to relay the CRT image to the writing stage of the liquid-crystal light valve modulator — a subsystem very unlike the spatial laser-beam modulation in the reading stage — ordinarily there must indeed be focusing in the writing stage.
- This beam is processed in two-dimensional sweeping devices 264 (such as polygon mirrors, galvanometer mirrors 5 etc.) to yield a two-dimensionally scanning laser-light beam 231.
- the two-dimensional sweep 264 is synchronized 265 with the one-dimensional sweep 20 of the laser beam on the associated light valve.
- All three laser-diode beams can be of the same color, and this "color" if preferred can be infrared or ultraviolet
- transmissive LCD modulators As mentioned earlier an LCD modulator (sometimes instead con- fusingly called a “transmissive liquid-crystal valve modulator”) is unsuited for direct use in large-format projectors.
- a transmissive LCD 332 (Fig. 17) should serve well. I believe that the image of the electrode pattern can be prevented from carrying through the liquid-crystal light valve to appear conspicuously in the projected output image
- a system of writing image information 463 (Fig. 18) as an electronic signal, directly to an electronic writing stage of a liquid-crystal light valve. It will be understood by those skilled in the art that the light valve now must be of a type which itself has an array of writing electrodes rather than a photosensitive writing surface .
- the electrodes are on the writing side of the opaque dielectric mirror in the light valve, they cannot be seen on the high-power laser writing-beam side of the valve. As noted above, the two stages are optically isolated.
- one-dimensional sweep 520 should be provided. As the primary images 573, 531 are not written incrementally, however, this sweep need not be synchronized with anything.
- motion-picture film Essentially the same system (Fig. 19) may be used to project greatly enlarged and powerful laser-beam images from motion-picture film. The film can be stepped through the image plane 560 using a generally conventional film gate and sprocket system (not shown) .
- Such a system can be used at very low light levels in the writing stage, thus permitting excellent image quality in an extremely large theater or outdoor-amphitheater without overheating the film.
- the system thereby avoids significant deterioration of — for example — a relatively old or otherwise fragile movie print.
- the amount of make-ready for each motion picture is minimal in terms of both effort and cost: the film is simply run through the writing stage of the projector and viewed in brilliant, vivid color on the jumbo screen.
- color separations 660 can be made (or in some cases may be available) in strip form from a motion-picture film print or master.
- the construction and the conventional operating mode of a liquid-crystal light valve ordinarily call for a positive optical input image, but modification to operate from a negative image would appear feasible.
- the three primary separations 660 may be . stepped through coordinated sprocket-and-gate mechanisms to project independent image sequences 663, 631 onto the photosensitive writing stages of liquid-crystal light valves.
- the remainder of the projection system is as before. Due to the need for mechanical synchronization, color registration in this form of the invention may be more troublesome than that in the single-print form (Fig. 19) .
- the projected images appear directly above and behind the people who are celebrating, performing etc.
- the pictures are typically of poor resolution, sharpness, contrast and even brightness.
- My invention can be used to project an extraordinarily high-quality live image of such celebrants, speakers etc. 766 (Fig. 21) who are at a stage or podium.
- a conventional telephoto lens 701 is pointed toward the subject 766, to acquire an image 760 in the usual way.
- the image 760 is redirected by folding mirrors 702, 703 to a filter system 762 such as in the Fig. 19 system — and thence in real time, and without any sort of electronic intervention or image storage — to a projection system as described earlier.
- a filter system 762 such as in the Fig. 19 system
- the same image, enormously enlarged, is then returned to appear 746 on a giant projection screen 747.
- the illustrated beam-turning system of folding mirrors (with a light-sealed tube enclo- sure) will commonly be preferable to a fiber-optic light pipe, since the latter may exhibit some visible granularity under the extremely high enlargement taken in the final projection stage.
- a very fine-fiber light pipe may serve. In either case it may be desired to provide purely optical switching, fading and vignetting arrangements — as well as mechanisms for pointing the lens 701 in different directions without losing either the image 766 or its orientation or focus.
- Subsystems (not illustrated) of this sort enable selection or combination of different real-time views in different directions from a single projector, for display on the screen.
- the mirrors 20 sweep the downward-directed beams 22 back and forth over the tops of the respective recollimators 23, but always within the apertures of those lenses, and into the entry faces 24 of polarizer-analyzer cubes 25.
- Each mirror moves in response to electronic control signals — which may be regarded as graphed at 20, Fig. 22 — di- rected to the corresponding mirror driver 21.
- control signals may be varied in such a way that the illustrated straight ramp 20 represents a constant rate of positional scan of the beam along each entry face 24 (and therefore along the modulator face and the projection medium) .
- This is theoretically preferable to a constant rate of signal change or a constant change of angle.
- the angle through which the beam sweeps over the recollimators 23, in view of the length of travel between the oscillating mirrors 20 and recol- limators, is small enough that ordinarily the scan speed is adequately constant in positional terms.
- each mirror 20 is advantageously controlled in correspondence with incremental writing of the image signal 31 to the CRT 32 — or to a liquid-crystal light valve electrode, laser diode, or other writing system such as enumerated in the preceding subsection "d” . Naturally this condition is inapplicable to full-frame or non- incremental writing systems (Figs. 19-21).
- Incremental writing where used, may typically be characterized by raster pixel and line advance states or signals 64 (Fig. 22), with a vertical blanking interval 67. It is known that the writing processes of a liquid-crystal light valve have a certain very short lag time, commonly on the order of a small number of pixel periods — and also a persistence period, typically corresponding to the time in which a few raster lines are written.
- the mirror sweep signal 20 (Fig. 22) is initially delayed by a time 68 (at left end of the drawing) related to the writing-process delay.
- Mechanical flyback 69 of the mirror may be effected during a like interval 68 (right end of the drawing) .
- That beam scans leftward and downward along the interface layer 26, not entirely by displacement but in part by
- lower writing rays 32q-32u respectively control certain reading-beam rays 22q-22u, 22q"-22u" (Fig. 23) in the vertical beam, and instead control shifted reading- beam rays 22s' -22v' (Fig. 24) in the displaced, angled reading beam.
- some reading-beam rays 22p that initially participate in the imaging of the writing-beam rays 32p will — in another instant — pass beyond these particular writing rays.
- a corresponding angled ray 22p' moves below the illustrated writing-beam region .
- the variation may be in the nature of a continuing acceleration of the pathlength difference from moment to moment, as the ray angle steepens ever more quickly with rotation of the mirror.
- the effect on beam coherence is not only a shift in absolute terms, i . e. in terms of the time for an image, ray to reach the screen, but also a perturbation differentially — which amounts to a disruption.
- the planar wavefronts of the beam acquire a cylindrical (but probably not a circular-cylindrical) twist.
- speckle For each position of the beam as described above, speckle is theoretically present — but the speckle pattern for each position of the beam is significantly different from that for every other position. Speckle patterns are understood to arise in the eye due to interferences from neighboring screen positions that are separated by distances only on the order of a wavelength of light. Even tiny changes in projection pathlength, changes on the order of the wavelength, therefore can significantly shift or totally change the speckle pattern.
- the speckle pattern therefore moves, and also changes, very quickly — far more rapidly than the eye and brain can follow it.
- the human vision mechanisms tend to average out the differences among the myriad diverse speckle patterns as they flash by, strongly decreasing the viewer's ability to distinguish or to perceive any single one pattern or cate- gory of patterns .
- An adjacent writing ray 32u (drawn with a lightweight line) we assume is instead very dim but not of zero energy, and — through the modulation processes of the valve — delays the corresponding return ray 34u (also in lightweight line) so that a portion 72u' of the same wavefront 72v' cannot quite reach the valve entry surface, at the above- defined "certain instant".
- the wavefront portion 72u' is thus second to the null portion 72v' (but only by a nose) , and roughly this same very small retardation will be preserved at the projection screen 47 for a portion 73u' of the same wavefront as the null wavefront 73v at the screen.
- the retardation in terms of physical distance will be slightly greater, making allowance for the difference in propagation speeds through the remainder of the modulator and through the air between cube and screen. (As will be understood, this retardation is shown greatly exaggerated in comparison with the schematically illustrated distance from the cube to the screen.)
- wavelength mixture Still further helpful in speckle suppression is the introduction of cyan light in conjunction with the long-wavelength (over 635 nm, and preferably between 635 and 650 nm; most preferably 647
- this en- hance ent may be due to a kind of admixture or dilution by. wavelengths that are present in relatively pure form but cannot constructively or destructively interfere with the primaries . It is also possible that those wavelengths themselves introduce some amount of another speckle component that helps to perceptually mask the speckle due to the primaries. In any event, this additional refinement in speckle suppression may be particularly helpful in, for example, portions of an image that are uniform in color and brightness — so that the light valve cannot provide effective disruption of coherence .
- the cross-sectional distributions illustrated are not merely one-dimensional — as for example from left to right across an image, or from top to bottom — but rather two-dimensional and with circular symmetry about the centerline £. Therefore it is the entire circumference, the annular region near the overall beam or aperture radius ⁇ r in the drawing, which is degraded. Particularly for square or rectangular images, as will shortly be seen, such a two-dimensional effect becomes difficult to correct or compensate.
- TM00 transverse mode Another common type of laser beam is a so-called "TM00 transverse mode". As shown, this sort of beam considerably better equalizes the intensity distribution at the center with respect to the intermediate regions that are, say, halfway out from the center to the beam edge. An intensity minimum appears at the center which (for reasons that will become clear momentarily) does not create a significant problem and in fact may be advantageous .
- the brightness cross-section commonly has a central declivity C analogous to that in the TM01 beam, and an intermediate region of brightness ripples R which an engineer or scientist might describe as "ringing down".
- the brightness distribution also exhibits a peripheral edge or limb L that falls very abruptly — just immediately inside the beam aperture — to a minimum that is essentially zero at the edge ⁇ r.
- Multimode beams as such were not invented by me, and are well known; however, they are a particularly valuable refinement of my invention. They provide a very acceptable approximation to the ideal tophat function TH mentioned earlier. All the fluctuations within the main body of the beam, i . e. inside the limb L, are relatively quite small as a fraction of the maximum brightness .
- a laser beam projected via a liquid-crystal light valve is subject to myriad erratic but strongly defined artifacts A (Fig. 29) . It has been suggested to me that these features arise from the polarization- and phase-based character of the light valve, as used with near-monochromatic laser radiation.
- the outer circle in the drawings may be regarded as slightly redefined. No longer does it represent the initial laser aperture ⁇ r of Figs . 25 , 25a but rather the effective aperture physically defined by the sharply cut-off peripheral limb L.)
- the best that can be done, the ideal, is to in- scribe the square within the circle as illustrated. In this relationship the diagonal of the square equals the diameter of the circle. If we call that common distance d, then the area of the square is d 2 /2 and the area of the circle is ⁇ d 2 / .
- One more-highly preferred format is 3:4 (Fig. 27) .
- the format (now rectangular) is inscribed within the circular source beam and calculate the two areas.
- the not-quite- uniform pattern of annular brightness rings when collapsed to a function along a diametral cross-section, will generally approximate a semicircular function 76 (Fig. 29) . If the original circular beam were entirely uniform, the pattern would be semicircular, necessarily remaining unchanged from the circular shape of the original beam.
- a preferable approach uses special refractive elements for the initial entry optics 18, 19 — or still more preferably a compound-curve molded mirror 120 (Fig. 10) — that may be customized to equalize both the energy distribution and the shape of the oval 22.
- a compound-curve molded mirror 120 Fig. 10
- this approach after masking off the wings 275 one can achieve a more nearly rectangular beam 222 with a very nearly flat distribution 276, calling for at most very minor compensation 277 — all as shown in the fourth view of Fig. 29.
- These approaches are desirable to avoid the need for an entirely separate optical compensator to impart the function 77 in the central view.
- an additional refinement can be included without significant cost: forcing the beam to scan at a substantially constant rate in terms of distance down the modulator, rather than in terms of the angle of the vibrating mirror or other deflector. Scanning at a constant rate along the modulator should track the writing beam at the input of the modulator more accu- rately. This improvement, however, will be significant only if the half anglG of the beam sweep (recollimator radius divided by distance from vibrating mirror to recollimator) is large enough to introduce a tracking error greater than one or two raster lines. In such a case, the skilled person will understand that for these purposes the rectilinear ramp 20 (Fig.
- the vertical position is roughly proportional to the sine of the beam angle; therefore the scan rate on the modulator can be equalized by driving the galvanometer or other deflector with its inverse function, namely an arcsine-f nction signal.
- angle changes as the arcsine of a constantly changing value kt, commonly written “sin -1 (kt)”
- screen position should vary approximately as sin ⁇ sin -1 (kt) ⁇ ⁇ kt, or in other words at a constant speed down the modulator frame.
- the projection throw (distance to the screen) is quite short and the screen quite tall (or wide) , a potential difficulty may arise in distortion and nonuniform illumination of the image due to the resulting relatively steep projection angle.
- the focusing of the beam on the screen by a field-curvature- correcting lens avoids these effects .
- image distortion and variation of image brightness — at the top or bottom of the screen with respect to the center.
- the distance to the screen is slightly greater, tending to spread the constant-angular-height beam over a greater distance — the beam cross-section varying with the reciprocal of the cosine of the off-axis angle of the beam relative to the system centerline.
- the beam therefore suffers a decrease in apparent brightness in each unit area, the brightness being proportional to the cosine. Furthermore at its top or bottom the screen is more strongly angled to the beam, tending to spread the beam even further on the screen. This effect introduces another factor of the reciprocal of the cosine in beam height along the screen. Considering the two effects together, the screen brightness must be proportional to the square of the cosine of the off-axis angle.
- persistence zone As mentioned earlier, optical energy is wasted if the reading beam illuminates portions of a liquid-crystal light valve where no image writing is taking place (or has recently taken place) in the image-input stage of the valve. Due to persistence effects in the valve, reading light can still be returned through an analyzer cube of my invention — and projected to a viewing screen — if that light reaches a raster line within a short time after that line has been written.
- Such a slot- shaped region which is in effect a persistence zone, is very similar in shape to the vertically collapsed beam 22, 222 (Fig. 29) .
- the persistence zone thus amounts to a fraction of the full image height. That fraction is generally between one tenth and perhaps one fifth or (with more margin for error) one quarter .
- AOMs Acoustooptic modulators
- Liquid-crystal "displays” or “devices” are not able to provide infinite sharpness. Projectors based on such devices accordingly are limited to forming an image on a simple screen in a conventional way. Most other laser applications involve either focusing the laser beam to a fine spot or projecting the beam unmodified. In effect the laser is manipulated and viewed from outside the beam, treated as if it were a tool or other object. My invention is thus the first to effectively open up a laser beam and manipulate it from the inside in such a way as to provide both (1) infinite sharpness and (2) a beam that is bright enough to effectively exploit that sharpness in a long-throw environment.
- the aperture d is typically on the order of 2H to 5 cm (one or two inches) although it can readily be made considerably larger, and the longest wavelength is preferably about 647 nm.
- my invention operates entirely within the near field, out to a kilometer (five-eighths of a mile)
- the preferred form of my invention is slightly complicated by the fact that I do not wish to transmit a cylindrical projection beam (i . e. a beam of constant cross- section) to the viewing screen or other medium. Rather I wish to use an expanding or conical/pyramidal beam 45, so that the image on the screen can be much larger than the projector optics.
- the character of this beam 45 somewhat defies conventional semantics, since it is factually a spreading or diverging beam — and it is of course a laser beam — but this "divergence" differs from the conventionally conceived "divergence" of a laser source.
- that term refers to diffraction-introduced degradation of the beam.
- the degradation of the beam is minuscule, and through provision of adequate aperture dimensions can be made negligible for virtually any desired projection distance — subject to availability of adequate laser power for the corresponding viewing distance and desired image size.
- I have used the term "expanding” rather than "diverging” .
- my invention is able to display sharp, bright images on projection media at extremely varied distances from the projector. This does not merely mean, as in the case of a conventional motion-picture projector, that my projector can be adjusted to show sharp moving pictures on a screen at any selected distance.
- the projector of my invention can project sharp pictures on a screen at any distance without adjustment — and furthermore that my projector can project sharp pictures on multiple screens or other objects at different distances simultaneously , and still without adjustment.
- Naturally adjustment may be desirable to change image size, but not for sharpness.
- a projector 101 can be positioned to project images onto a group of buildings 147 that are at distinctly different distances from the projector.
- the buildings may include one structure 147d which has a surface generally at right angles to the center of the projection beam 145, another building 147e that is further away and steeply angled to the beam, so that the beam almost grazes the building, and a third building that is still further away and is a dome .
- the first-mentioned structure 147d also has a side face that is essentially parallel to the beam, and which the beam only grazes in passing. (In the grid-marked perspective section of the drawing at far left, the grid lines are intended to show the contours of the structures — not a grid of the projected image.)
- the projected images may be seen from any of a great number of observer positions 178.
- the ob- 5 server may be able to see grain in the original photograph (or copy) 560.
- the observer 178c may be able to perceive the focal limitations of the original pickup lens 701.
- Brightness too is distorted by projection distance, and such peculiarities can be seen by such an observer who is close to the projection medium.
- the designers select and arrange objects within the image frame so that desired visual effects will appear on the various structures. For instance the stretched appearance of image elements on the angled building 147e or on the
- dome 147f may be used to dramatic effect — or alternatively may be compensated by providing a carefully controlled compression of the image in that area — if it is known that an important fraction of the audience is to see the image from a vantage which gives that stretched effect. If de-
- brightness in various image portions can be boosted or suppressed (preferably by manipulating the original image data) to produce natural appearance from such a vantage.
- the example here is at an intermediate scale. Much larger projection configurations are feasible, as for instance projection from far greater distances into the range of kilometers.
- a single projected image may be carefully designed, in anticipation of a specific position for the projector 301 in relation to a particular assemblage of such media, so that for example no image element will be projected toward regions of space where no desired projection medium 347 is expected.
- the projection beam may contain only image elements 346d, 346e, 346f that are respectively aligned with the flowing water surfaces 347d, 347e, 347f.
- Naturally such dramatic effects are optional, but can for instance include projecting a moving image of one person — a dancer, for example, or a clown or a soldier respec- tively — onto each of the differently spaced water sprays 347d, 347e or sheets 347f .
- Narrative or musical effects can issue from a respective loudspeaker or live performer positioned at each image.
- water and other media can be used in other forms such as clouds, fog and ice.
- the surface itself is independently controllable — as for example in the case of computer-controlled fountains and other sprays — additional useful special effects can be obtained even if plural surfaces are aligned along a common projection axis.
- the closer fountain can be turned off so that all the light bypasses the position of that fountain and proceeds to the position of another fountain that is farther from the projector.
- effects can be made more subtle or interesting by only feathering or otherwise changing the density or other character of the first spray — rather than turning it completely on or off — to shift the balance, progressively, between projection primarily onto that spray or primarily onto the more-remote spray.
- images may be either directed to water elements that are laterally spaced apart, or partially projected through one such element to another behind it.
- the latter arrangement may also be mimicked in nonliquid elements that are nevertheless translucent or only partially reflective, such as stage scrims 447d, 447e (Fig. 33) .
- stage scrims 447d, 447e Fig. 33
- the more- forward partially transmissive surfaces 347d, 347e, 447d, 447e typically can reflect to the audience only filmy or gauzy but nearer images, while the rearwardmost surfaces 347f , 447f may be used to reflect perhaps more solid-seeming but also more distant images.
- the degree of transparency or translucency of a water surface or scrim can be adjusted by the density of the droplets, mesh or weave, thereby adjusting the balance between brightnesses of the nearer and more distant images.
- all the images 346, 446 are sharp. If the forward scrims 447d, 447e extend across an entire stage (e. q. behind a proscenium 479) , so that the projection beam 445 can reach the rearward scrims only by passing through the forward ones, opportunities for separation of images in space are somewhat restricted.
- Still another class of projection media are living things. Particularly interesting image effects may be obtained by projection on trees 547 (Fig. 34), vines, bushes, and other plants. As shown in the drawing, an image set may be prepared for projection that contains components at roughly left, right and center that are aligned for projection onto respective trees 547d, 547e, 547f.
- the show may be viewed from near the position of the projector 501, or if preferred from an audience position somewhat off to one side as actually demonstrated by the illustration.
- different moving images may appear sharply on each of the trees — made, for instance, from dramatic film clips of faces (e. g. statesmen, actors, singers, storytellers), or perhaps of cartoon characters, animals, fish, birds etc.
- axially spaced natural objects living creatures
- living creatures In many of the foregoing exemplary embodiments of my invention I have suggested projecting images of living people onto inanimate objects.
- Another creative form of my invention encompasses instead projecting images onto living people 647 (Fig. 35) .
- images 646 of inanimate (or animate) objects such as flags, swords, cannons, or even scenery — might be projected onto groups of people. This can be done in such a way as to simultaneously illuminate the people and superimpose upon them images of emblems or icons related to their dramatic roles.
- a sharply defined image of a peacepipe (not shown) , with smoke curling above it and a fluttering feather below, is projected on the upper group.
- interchannel 240 9.45 offset D between the red and blue channel mirror centerlines 120 4.72 offset E between the red and green chan- nel mirror centerlines 120 4.72 offset F between the blue and green channel mirror centerlines
Abstract
Description
Claims
Priority Applications (3)
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MXPA00011926A MXPA00011926A (en) | 1998-05-01 | 1999-04-30 | Laser projection apparatus with liquid-crystal light valves and scanning reading beam. |
CA2372833A CA2372833C (en) | 1998-05-01 | 1999-04-30 | Laser projection apparatus with light valve and scanning reading beam |
AU41822/99A AU4182299A (en) | 1998-05-01 | 1999-04-30 | Laser projection apparatus with liquid-crystal light valves and scanning readingbeam |
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US09/071,398 | 1998-05-01 | ||
US09/071,398 US6183092B1 (en) | 1998-05-01 | 1998-05-01 | Laser projection apparatus with liquid-crystal light valves and scanning reading beam |
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WO1999060443A3 WO1999060443A3 (en) | 2000-01-20 |
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US (4) | US6183092B1 (en) |
AU (1) | AU4182299A (en) |
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US6971575B2 (en) | 1999-06-07 | 2005-12-06 | Metrologic Instruments, Inc. | Hand-supportable planar laser illumination and imaging (pliim) device employing a pair of linear laser diode arrays mounted about an area image detection array, for illuminating an object to be imaged with a plurality of optically-combined spatially-incoherent planar laser illumination beams (plibs) scanned through the field of view (fov) of said area image detection array, and reducing the speckle-pattern noise power in detected 2-d images by temporally-averaging detected speckle-noise patterns |
US6991165B2 (en) | 1999-06-07 | 2006-01-31 | Metrologic Instruments, Inc. | Method of speckle-noise pattern reduction and apparatus therefor based on reducing the temporal coherence of the planar laser illumination beam before it illuminates the target object by applying temporal intensity modulation techniques during the transmission of the plib towards the target |
US7090133B2 (en) | 1999-06-07 | 2006-08-15 | Metrologic Instruments, Inc. | Method of and apparatus for producing a digital image of an object with reduced speckle-pattern noise, by consecutively capturing, buffering and processing a series of digital images of the object over a series of consecutively different photo-integration time periods |
US7028899B2 (en) | 1999-06-07 | 2006-04-18 | Metrologic Instruments, Inc. | Method of speckle-noise pattern reduction and apparatus therefore based on reducing the temporal-coherence of the planar laser illumination beam before it illuminates the target object by applying temporal phase modulation techniques during the transmission of the plib towards the target |
US6742707B1 (en) | 2000-06-07 | 2004-06-01 | Metrologic Instruments, Inc. | Method of speckle-noise pattern reduction and apparatus therefor based on reducing the spatial-coherence of the planar laser illumination beam before the beam illuminates the target object by applying spatial phase shifting techniques during the transmission of the plib theretowards |
US7131586B2 (en) | 2000-06-07 | 2006-11-07 | Metrologic Instruments, Inc. | Method of and apparatus for reducing speckle-pattern noise in a planar laser illumination and imaging (PLIIM) based system |
US7077319B2 (en) | 2000-11-24 | 2006-07-18 | Metrologic Instruments, Inc. | Imaging engine employing planar light illumination and linear imaging |
US7140543B2 (en) | 2000-11-24 | 2006-11-28 | Metrologic Instruments, Inc. | Planar light illumination and imaging device with modulated coherent illumination that reduces speckle noise induced by coherent illumination |
US7743990B2 (en) | 2000-11-24 | 2010-06-29 | Metrologic Instruments, Inc. | Imaging engine employing planar light illumination and linear imaging |
Also Published As
Publication number | Publication date |
---|---|
US6183092B1 (en) | 2001-02-06 |
US20010046033A1 (en) | 2001-11-29 |
CA2372833A1 (en) | 1999-11-25 |
US8113660B1 (en) | 2012-02-14 |
MXPA00011926A (en) | 2002-10-17 |
US20050057727A1 (en) | 2005-03-17 |
US7055957B2 (en) | 2006-06-06 |
WO1999060443A3 (en) | 2000-01-20 |
CA2372833C (en) | 2013-01-15 |
US6910774B2 (en) | 2005-06-28 |
AU4182299A (en) | 1999-12-06 |
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